The present disclosure relates to a high intensity discharge lamp (HID). More particularly, it relates to a metal halide lamp having high efficiency, good color rendering and high color temperature.
Metal halide lamps typically have a quartz, polycrystalline alumina (PCA), or a single crystal alumina (sapphire) arc discharge vessel filled with a mixture of gases, which may be surrounded by a protective envelope. The fill includes light emitting elements such as sodium and rare earth elements, such as scandium, indium, dysprosium, neodymium, praseodymium, and cerium in the form of a halide, with mercury, and generally an inert gas, such as krypton, argon or xenon. Metal halide lamps are disclosed, for example, in U.S. Pat. Nos. 4,647,814; 5,929,563; 5,965,984; and 5,220,244. While lamps of this type having an outer jacket or envelope have been formed with relatively high color temperatures, unjacketed arc tubes (in which the discharge chamber is in direct contact with the atmosphere, generally have a much lower color temperature or poor color rendition index (CRI). U.S. Pat. Nos. 5,138,227 and 5,486,737 disclose double ended lamps which operate at high wattage.
The entertainment industry desires bright, white light compact sources that enable efficient collection and focusing of the light to produce multiple effects such as the projection of Gobos, color patterns, and moving lights. However, at high wall loadings, color temperatures are generally low.
There remains a need for a lamp which can operate at high power and provide both high color temperatures and good color rendering for such applications.